This invention relates to communications controller for a radio communications system. In most cases of the related art, a mobile station communicates with one base station during normal calls. However, during a handover, a mobile station is connected to a plurality of base stations. The background includes U.S. Pat. No. 5,101,501, U.S. Pat. No. 5,267,261, U.S. Pat. No. 5,088,108, U.S. Pat. No. 5,109,528, U.S. Pat. No. 5,327,577 and Japanese Translation of Unexamined PCT application No. 10-511835.
While a mobile station communicates with one base station, the radio waves (or carrier) from that mobile station are capable of communicating with other base stations. In CDMA (code-division multiple access), for instance, the number of base stations that can simultaneously connect with a particular mobile station depends on the extent of the interfering power emissions. The power interference is small if there are not many other mobile stations, and using the radio waves (or carrier), a particular mobile station can make simultaneous contact with a plurality of base stations.
Generally, in a radio communications system, the service area of a base station overlaps with adjacent base stations to ensure the continuity of the communications service. Handovers are performed when a mobile station is in these overlapping areas. The mobile station makes a link connection with a plurality of base stations during a handover, and the same data contents are transmitted and received in each link. Transmitting the same data allows obtaining the site diversion effect.